Musnad Ahmad 2:127

Abu Nuh Qurrad narrated to us, Ikrimah ibn Ammar informed us, Simak al-Hanafi Abu Zumayl narrated to me, Ibn Abbas narrated to me, Umar ibn al-Khattab narrated to me, who said: When the day of Badr arrived, the Prophet (peace and blessings of Allah be upon him) looked at his companions, and they were three hundred and some odd men, and he looked at the polytheists, and they were a thousand and more. The Prophet (peace and blessings of Allah be upon him) faced the Qibla, then stretched out his hands, while wearing his cloak and his lower garment, then said: "O Allah, where is what You promised me? O Allah, fulfill what You promised me. O Allah, if You destroy this band of the people of Islam, You will never be worshipped on earth again." He continued to beseech his Lord, the Mighty and Majestic, and call upon Him until his cloak fell off. Abu Bakr came to him, took his cloak, placed it back upon him, then embraced him from behind and said: "O Prophet of Allah, this pleading with your Lord is enough, for He will fulfill for you what He promised you." Then Allah, the Mighty and Majestic, revealed: {When you were seeking help of your Lord, and He answered you, "Indeed, I will reinforce you with a thousand from the angels, following one another"} [Al-Anfal: 9]. When that day came and they met, Allah, the Mighty and Majestic, defeated the polytheists. Seventy of them were killed, and seventy of them were taken captive. The Messenger of Allah (peace and blessings of Allah be upon him) consulted Abu Bakr, Ali, and Umar. Abu Bakr said: "O Prophet of Allah, these are the cousins, the kin, and the brothers. I see that you should take a ransom from them, so that what we take from them may be a strength for us against the disbelievers, and perhaps Allah will guide them, and they will be a support for us." The Messenger of Allah (peace and blessings of Allah be upon him) said: "What do you see, O son of al-Khattab?" I said: "By Allah, I do not see what Abu Bakr saw. Rather, I see that you should enable me to deal with so-and-so—a relative of Umar—so I may strike his neck, and enable Ali to deal with Aqil so he may strike his neck, and enable Hamza to deal with so-and-so, his brother, so he may strike his neck, until Allah knows that there is no softness in our hearts toward the polytheists. These are their chiefs, their leaders, and their commanders." The Messenger of Allah (peace and blessings of Allah be upon him) inclined toward what Abu Bakr said and did not incline toward what I said, so he took the ransom from them. When the next day came, Umar said: I went early to the Prophet (peace and blessings of Allah be upon him), and he was sitting with Abu Bakr, and they were both weeping. I said: "O Messenger of Allah, tell me what makes you and your companion weep? If I find a reason to weep, I will weep, and if I do not find a reason to weep, I will feign weeping for your sake." The Prophet (peace and blessings of Allah be upon him) said: "It is because of what your companions proposed to me regarding the ransom. Your punishment was presented to me closer than this tree"—pointing to a nearby tree. And Allah, the Mighty and Majestic, revealed: {It is not for a prophet to have captives until he has thoroughly subdued the land} up to: {If not for a decree from Allah that preceded, you would have been touched by what you took} [Al-Anfal: 67-68] of the ransom. Then He made the spoils of war lawful for them. When the day of Uhud came the following year, they were punished for what they had done on the day of Badr by taking the ransom. Seventy of them were killed, the companions of the Prophet (peace and blessings of Allah be upon him) fled from the Prophet (peace and blessings of Allah be upon him), his incisor tooth was broken, the helmet was smashed on his head, and blood flowed down his face. Allah, the Exalted, revealed: {Why, when a disaster struck you, although you had struck [the enemy] with one twice as great, did you say, "From where is this?" Say, "It is from yourselves." Indeed, Allah is over all things competent} [Al-Imran: 165], because of your taking the ransom.